[PATCH] mmc: Add power stabilization delay in mmc_power_on()

[ziniu.wang_1 at nxp.com]

From: Luke Wang <ziniu.wang_1 at nxp.com>

After enabling vmmc supply, add 10ms delay to allow voltage to
stabilize before SD initialization starts. Without this delay,
some SD cards fail to initialize because the initial clock cycles
are sent while power is still ramping up.

Signed-off-by: Luke Wang <ziniu.wang_1 at nxp.com>
---
 drivers/mmc/mmc.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
index bf82c515600..97037722fe1 100644
--- a/drivers/mmc/mmc.c
+++ b/drivers/mmc/mmc.c
@@ -2878,6 +2878,12 @@ static int mmc_power_on(struct mmc *mmc)
 			printf("Error enabling VMMC supply : %d\n", ret);
 			return ret;
 		}
+
+		/*
+		 * Wait for power supply to stabilize before sending
+		 * initial clock cycle.
+		 */
+		mdelay(10);
 	}
 
 	if (mmc->vqmmc_supply) {
-- 
2.34.1